HYDROPROCESSING OF BIOMASS DERIVED OILS TO TRANSPORTATION FUELS

Abstract

Energy is the foundation of economic and infrastructure development. Environmental concerns, global energy requirement, and declining fossil fuel reserves have boosted energy research on alternatives source from conventional fossil fuels to an alternative renewable and sustainable sources. Based on the availability of biomass feedstock, first generation, second generation, and third generation are the classification of biofuels. First generation biofuels are bio-ethanol and bio-diesel, which are produced by using biological process (fermentation) and chemical-process (trans-esterification) from edible sources like sugar, starch and plant seeds oils (vegetable oils) etc. The production of first-generation biofuels is very less in comparison to the requirement in terms of conventional refineries/fossil fuels, so there is an issue with demand vs. supplies, i.e. competition with the food industry and fuels, which may raise ethical questions. It also doesn’t give the drop-in-fuel quality. Research now strongly focuses on the so-called second-generation biofuels. Second generation biofuels give attention to the thermal conversion of non-edible biomass sources. The thermal conversion has mainly four processes: combustion, gasification, hydrothermal liquefication and pyrolysis. Combustion is already widely practiced. Gasification has higher efficiency as compared to combustion. It has a high level of interest, to produce bio-syngas to generate methanol or transportation fuels like gasoline, kerosene and diesel. Hydrothermal liquefaction (HTL) of biomass has been done in presence of solvents at various temperature and pressure. Pyrolysis process decomposes the biomass in the absence of oxygen to generate vapors (pyrolysis vapor) and aerosols with some char/coke (bio-char) at high temperature, on condensation of pyrolysis vapor a liquid has been obtained, called pyrolysis oil/bio oil. The Third-generation biofuels concern about fast-growing feedstokes, requires less maintenance/nutrient and low cost for production. It has tendency to regenerate in the less fertile soil, and resistance to extreme weather conditions. The third-generation ii biomass includes microalgae and macroalgae. Marine biomass such as seaweed, hyacinth, caltrop diatoms, duckweed, and algae have a strong domain for the production of biofuels. In recent year Aquatic biomass (microalgae) is considered third-generation biomass and advanced biofuel feedstock due to their perennial and inherent growth, high growth rate and areal productivity as well as no competency with arable land and crops for space, sunlight, and nutrients. Algal biomass can produce different types of biofuels, including bioethanol, biodiesel, syngas, gasoline, kerosene/jet oil and diesel (green diesel). Some of them biofuels, like gasoline, kerosene/jet oil and diesel (green diesel) can produce by hydroproceesing, a refinery technique for upgradation of biomass derived oil (pyrolysis oil/bio oil and algae oil/lipids) by using batch reactor as well as continuous fixed bed (microchannel) reactor. For convenience, the work embodied in the thesis has been divided into the following chapters: First chapter This chapter is introductory one and presents general remarks on first, second, and third generation biofuels. This chapter also deals with hydroprocessing of biomass-derived oil to transportation fuels. Updated literature survey has also been included here. Second chapter This chapter deals with the production of transportation fuels (gasoline, kerosene, and diesel) by hydroprocessing of mixture of gas oil (GO) with heavy, dark viscous pyrolysis oil/ bio oil liquid (BO) obtained from waste de-oiled jatropha curcas seeds cake (JCC). A sulfided cobalt–molybdenum phosphorus/aluminum oxide (CoMoP/Al2O3) catalyst was studied in the hydroprocessing of bio-oil (BO) obtained from the pyrolysis of de-oiled Jatropha curcas seed cake. Hydroprocessing was carried out with different ratios of GO and BO with sulfided cobalt–molybdenum phosphorus/aluminum oxide (S-CoMoP/Al2O3) catalyst. The oxygen content in the products was reduced to trace amounts after hydroprocessing. A clear liquid product having 2–16 % gasoline, 30–35 % iii kerosene/jet oil and 35–44 % diesel has been produced by co-processing of BO with refinery GO in various ratios. This liquid have 50–60 % alkanes, 10–45 % cycloalkanes, and 1–10 % aromatics with negligible amount of char. Hydroprocessing of 100 % BO produce 10 % gasoline, 30 % kerosene/jet oil and 30 % diesel. This liquid has 15 % of alkanes, 15% cycloalkanes, and 45 % aromatics. A maximum amount of kerosene (41%) was obtained at 375oC and 75 bar from 100 % BO, with a small amount of char (1.5%) deposited on the catalyst. In comparison, over sulfided CoMo/Al2O3 catalyst (without P promoter) only 31% of kerosene was produced, with 17% char, using similar reaction conditions. The advantage of this work is that transportation fuels can be produced by using a single catalyst instead of other expensive multi-catalyst processes such as hydrodeoxygenation with noble metals followed by cracking. Third chapter This chapter discusses the production of transportation fuels (gasoline, kerosene, and diesel) by hydroprocessing of aqueous-phase of pyrolysis oil obtained from de-oiled jatropha curcas seeds cake (JCC), by using sulfided NiMo/SiO2-Al2O3 catalyst coated in a microchannel reactor. The oxygen contents of the dissolved organic compound in the aqueous-phase were reduced to trace amount after hydroprocessing. Clear organic hydrocarbon phase product obtained after hydroprocessing contained 5-45% gasoline (<C9), 5-60% kerosene (C9-C14), 15-40% diesel (C15-C18). This liquid has 15-65% alkanes, 0-5% polyaromatic hydrocarbons (PAH) with negligible amount of cycloalkanes and aromatics. The unreacted feedstock and residues was 30-75%. Maximum hydrocarbon yield (~65%) was obtained at 375oC, 0.25 LHSV, and 70 bar. The water obtained after hydroprocessing contained little organics (<5%). Microchannel reactor has the advantages of portability, easy scale-up, better heat and mass transfer characteristics, high reaction throughputs, precise control of hydrodynamics. The good thing about this work is that transportation fuels can be produced by using small modular microchannel reactors (with catalyst coating inside the channels) compared to using largely fixed bed reactors. Additionally, this process improves the economics of processing bio-oils by utilizing its aqueous-phase (containing iv ~30% inseparable soluble organics) to produce hydrocarbon fuels. Fourth Chapter This chapter deals with the production of transportation fuels from triacylglycerides neutral lipids (TAGs) extracted from marine microalgae algae Nannochloropsis sp by hydroprocessing over sulfided cobalt molybdenum phosphorus/aluminum oxide (S-CoMoP/Al2O3) catalyst in a batch reactor at 300–375 °C with H2 at 50–120 bar. A clear light yellowish green product was obtained, containing 6–26 % gasoline, 35-50 % kerosene, 8–40 % diesel. This liquid having 10–80 % alkanes, 1–10 % cycloalkanes, and 5–35 % aromatics, with a maximum of 10% char formation. Power law kinetic model was validated with experimental results. A kinetic study shows a pseudo 1st order reaction with respect to the neutral algae lipids oil concentration, with the activation energy for algal oil conversion was 14.96 kJ/mol. Activation energies for the formation of diesel (125 kJ/mol) and kerosene (146 kJ/mol) were higher than for the heavy hydrocarbons such as PAH (7 kJ/mol) and alkanes (64 kJ/mol) products. This study investigates for the first time the hydroprocessing of crude lipids extracted from the commercially relevant marine microalga Nannochloropsis sp. over a sulphided form of CoMoP/Al2O3 catalyst. Finally, summary and conclusions based on the achievements are presented.